target-arm/arm-semi.c: Fix SYS_HEAPINFO for 64-bit guests

target-arm/arm-semi.c: Fix SYS_HEAPINFO for 64-bit guests

SYS_HEAPINFO is one of the few semihosting calls which has to write
values back into a parameter block in memory.  When we added
support for 64-bit semihosting we updated the code which reads from
the parameter block to read 64-bit words but forgot to change the
code that writes back into the block. Update it to treat the
block as a set of words of the appropriate width for the guest.

Signed-off-by: Peter Maydell <[email protected]>
Message-id: 1466783381[email protected]